81361987 has 4 divisors (see below), whose sum is σ = 92985136. Its totient is φ = 69738840.

The previous prime is 81361981. The next prime is 81361991. The reversal of 81361987 is 78916318.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 81361987 - 2⁷ = 81361859 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81361981) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5811564 + ... + 5811577.

It is an arithmetic number, because the mean of its divisors is an integer number (23246284).

Almost surely, 2^81361987 is an apocalyptic number.

81361987 is a deficient number, since it is larger than the sum of its proper divisors (11623149).

81361987 is a wasteful number, since it uses less digits than its factorization.

81361987 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11623148.

The product of its digits is 72576, while the sum is 43.

The square root of 81361987 is about 9020.0879707462. The cubic root of 81361987 is about 433.3184510997.

The spelling of 81361987 in words is "eighty-one million, three hundred sixty-one thousand, nine hundred eighty-seven".